Selenium rectifier



Feb. 7, E50 w. E. BLACKBURN 2,496,432

SELENIUM RECTIFIER Filed May 21, 1946 wuTNEssES: INVENTOR E a Wayne'.laclfbum. @u

Patented Feb. 7, 1950'.

SELENIUM RECTIFIER Wayne E. Blackburn, Wilkinsburg, Pa., assigner toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporationof Pennsylvania Application May 21, 1946, Serial No. 671,176

(Cl. l75-366) 4 Claims.

My invention relates to selenium rectiers, and, in particular, relatesto an improved method of rendering the junction between the selenium andthe counterelectrode unilaterally conductive. A number of differentprocedures for improving the unilateral nature of the above-mentionedjunction have been employed in the prior art, such procedures beingcommonly referred to as the production of the blocking layer at theselenium surface.

One object of my invention is, accordingly, to provide an improved typeof selenium rectifier.

`Another object of my invention is to provide an improved type ofblocking layer for selenium rectiers.

Still another object of my invention is to produce a blocking layer forselenium rectifiers, which is particularly effective in withstandinghigh inverse voltages.

Other objects of my invention will become apparent upon reading thefollowing description, taken in connection with the single figure ofdrawing which is a cross-sectional` view of a selenium rectifierembodying the principles of my invention.

Referring to the drawing, a suitable form in which the principles of myinvention may be embodied comprises a base plate I which may be ofsteel, and which is preferably nickel-plated and sand-blasted on thesurface. One face of the plate I is coated with a layer 2 of seleniumwhich may be applied by dipping the plate I in a molten bath ofselenium, and thereafter rotating the plate on a suitable spindle, or.other device, to throw off the excess of selenium, while molten, bycentrifugal force. The free surface of the selenium is then coated, inaccordance with my invention, with a thin film 3 of one of the followingmetals: germanium, silicon, magnesium, aluminum, cerium, berryllium,indium. This thin 1ayer of one of the above metals may, for example, beapplied by vaporizing the metal and condensing it in an evacuatedcontainer. The nlm is preferably made thin enough to permit diiusionthrough it by the materials of a counterelectrode l which issubsequently applied by metal spraying cadmium. or an alloy ot cadmiumand tin. For example, the thickness of the above-mentioned thin nlm ofmetal may be about one micron.

After deposition of the counterelectrode I, the unit is heat-treated ata temperature of about 200 C. for a period of about 2 hours. The unitmay then be electrically formed by impressing,

als

2 between the terminals I and 4, a self-rectified sixty-cycle voltage ofabout 30 volts for a period of about one hour. Thereupon, the element issuitable for use in any of the standard connections of rectifier unitswell-known in the art.

I claim as my invention:

1. The method of improving the unilaterallyconductive properties of thejunction between the selenium and the counterelectrode in a seleniumrectifier which comprises superposing a thin layer of metal selectedfrom the group consisting of magnesium, aluminum and beryllium on thesurface of the selenium and superposing on said layer a counterelectrodecontaining cadmium.

2. The method of producing a conducting element for electric circuitswhich comprises coating a base plate of metal with a layer of selenium,coating the free surface of the selenium with a thin layer of one ormore metals selected from the group consisting of magnesium, aluminumand berryllium; depositing a layercontaining cadmium on the free surfaceof said layer, and heat-treating the unit thus formed.

3. An electric circuit element comprising a base plate having a layer ofselenium deposited on a portion of its surface, a thin layer of one ormore metals selected from the group consisting of magnesium, aluminumand beryllium and a counterelectrode containing cadmium superposed onthe free surface of the last-mentioned layer.

4. An electric circuit element comprising a base plate --having a layerof selenium deposited on a portion of its surface, a layer of one ormore metals selected from the group consisting of magnesium, aluminumand beryllium and a counterelectrode containing cadmium superposed onthe free'surface of the last-mentioned layer, said layer being thinenough to permit diffusion through it by materials from saidcounterelectrode.

WAYNE E. BLACKBURN.

REFERENCES CTTED The following references are of record in the tile ofthis patent:

UNITED STATES PATENTS Number Name Date 2,096,170 Geisler oct. 19, 19372,361,157 Thompson Oct. 24, 1944 2,380,880 Thompson July 31, 1945

4. AN ELECTRIC CIRCUIT ELEMENT COMPRISING A BASE PLATE HAVING A LAYER OFSELENIUM DEPOSITED ON A PORTION OF ITS SURFACE, A LAYER OF ONE OR MOREMETALS SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, ALUMINUM ANDBERYLLIUM AND A COUNTERELECTRODE CONTAINING CADMIUM SUPERPOSED ON THEFREE SURFACE OF THE LAST-MENTIONED LAYER, SAID LAYER BEING THIN ENOUGHTO PERMIT DIFFUSION THROUGH IT BY MATERIALS FROM SAID COUNTERELECRODE.